markup modules I've written

Module whose design I put the most thought into:
Pod::PXML.
It turns Pod into an XML instance, and back. The hard part was the specifics of
the instance's doctype. What a "=item" looks like, etc.

Hard because there's so many ways to do it; some better for some things,
some better for others. Compare its doctype
to the much more verbose doctype from Matt Sergeant's
Pod::XML. Now that
I've written perlpodspec and gotten pod more sorted in my mind, I'm beginning
to think Pod::PXML should be a tiny bit more like Pod::XML's doctype.
Notably, now that I have stipulated all the kinds of "=over...=back" regions there
are, and decided that the first paragraph after the =over should dictate the
type, I sort of wish that an "=over / =item *... =back" region would turn
into different elements than an "=over =item 1.... =back" region would.
Maybe next time. First to fix some annoyances in Pod::Tree,
I guess.